1) Field of the Invention
The present invention relates generally to cotton harvesters and, more specifically, to cotton picker doffer column structure having increased strength and doffer support.
2) Related Art
Cotton harvesters of the spindle type such as the John Deere model 9960 Cotton Picker include row units with upright picker drums having spindle bars defining rows of picking spindles. Adjacent each of the picker drums is a doffer column with a plurality of doffers supported on a shaft for rotation directly above the rows of spindles to unwrap cotton from the spindles and direct the cotton towards conveying structure on the row unit. The doffers have apertured metal support plates which are horizontally disposed and vertically spaced on a doffer shaft using thin walled cylindrical spacers. The spacers have an inner diameter approximately equal to but slightly larger than the outer diameter of the shaft and are slid over the shaft between doffers. A doffer column nut at one end of the column sandwiches the support plates between adjacent spacers. Frictional engagement between the plates and the spacers causes the doffers to rotate with the doffer shaft.
Several problems exist with conventional doffer columns with the cylindrical spacers. The small, radially inward contact area between the spacers and the support plates of the doffers limits torque, and wear of the spacers and the plates can occur if the doffers slip. Doffer vibration and instability can also occur, particularly when doffer speeds and/or doffer column lengths are increased and the typical doffer operating speed approaches the critical speed. The relatively small radius doffer shaft is subject to heavy loads and off-axis bending which stresses the entire column and the bearings supporting the column. The spacers provide some shaft reinforcement which is limited because of the small spacer radius.